ALUMDTUM

106

ALVA

composition of granite, traps, slates, schists,
clays, loams and other rocks. The porcelain
clays and kaolins contain about half their
weight of this earth, to which they owe their
most valuable properties. It has a strong
affinity for coloring matters, which causes it
to be employed in the preparation of the
colors called lakes, used in dyeing and calico
printing. It combines with the acids and
forms numerous salts, the most important of
which are the sulphate and acetate, the latter
of extensive use as a mordant. In its native
state alumina is called corundum. When
crystallized it appears as ruby or sapphire.

Related Articles* Consult the following
titles for additional information:
Emery Sapphire

Corundum Topaz

Ruby

ALU'MINUM, or ALUMINIUM, a

bluish-white metal discovered in 1827, and
nest to silicon and oxygen the most widely
distributed element in the earth's crust.
Aluminum is a little more than two and one-
half times heavier than water. It does not
tarnish when exposed to the air, is very
ductile and malleable and is the most sono-
rous of all metals. It melts at 1160 °F. It is
nowhere found native, but is the basis of
clay, which is its oxide.

Uses. The uses of aluminum are rapidly
increasing. It is a good conductor of elec-
tricity and because of its lightness takes the
place of copper occasionally in the construc-
tion of electric lines. One of its most im-
portant uses is in the manufacture of steel,
since the addition of a small quantity of
aluminum greatly improves the quality of
the steel. It is also used in the manufacture
of numerous household utensils, for which
it is especially suited, since it is light, durable
and is not easily acted upon by acids. Smaller
articles, like hairpins, thimbles, combs, etc.,
are frequently made of it. There are nu-
merous alloys of aluminum and other metals,
such as aluminum bronze, an alloy with cop-
per, and magnalium, an alloy with mag-
nesium. Most of these alloys take a high
polish and are valuable for ornamental work.
Other alloys are utilized in the manufacture
of aeroplanes, boats and automobiles.
Aluminum gold, which is a compound of
aluminum and copper closely resembling
gold, is often used in the manufacture of
watch cases and cheap jewelry. While it
is bright when new, it soon tarnishes and is
almost worthless for ordinary purposes.

Manufacture. Because of the difficulty
in separating aluminum from its compounds
it is only recently that it has been obtained
in such quantities as to bring it into prac-
tical use. It is now obtained from bauxite
(see BAUXITE) by subjecting this mineral
to the heat of the electric arc. The operation
is carried on in furnaces constructed specially
for the purpose. The furnace is practically
a huge crucible made of blocks of carbon.
In the bottom of the crucible is a small tap-
hole, where the melted aluminum may be
drawn out.
The positive electrode is constructed of
heavy carbon plates so as to form a prism.
This is attached to a chain and a derrick
so it can be lowered into the crucible as fast
as the end burns off. Before the process be-
gins, pieces of copper are thrown into the
crucible to form the negative electrode. The
bauxite is shoveled in through openings made
for the purpose. When the electric circuit
is completed, a terrific heat is produced which
causes the bauxite to give up its aluminum.
This runs down to the bottom of the crucible
and is drawn of: through the tap-hole. The
bauxite is fed into the crucible as fast as it
is reduced, and the process continues until
the carbon electrode has been entirely con-
sumed. An ordinary furnace will produce
about 400 pounds in twenty-four hours.
Aluminum smelters are located at Niagara
Falls, Pittsburgh, Pa., Shawinigan Falls,
Que., and Arvide, Que.
When first prepared for commercial use
aluminum sold for $90 per pound, a price
which made its wide employment impossible.
Through perfected methods of manufacture
the price fell within a year to $2 per pound,
and later to twenty to thirty cents.
AI/UM BOOT, the name given in America
to two plants on account of the remarkable
astringency of their roots, which are used
for medical purposes. One of these plants
belongs to the geranium group, and the other
to the saxifrage family. The tincture of the
root of the former is used to cure sore throat
and mouth ulcerations. The root of the lat-
ter has been found valuable in the prepara-
tion of a wash for wounds and ulcers.
ALVA, M'vah, or ALBA, FERDIKAKD
ALVAREZ DE TOLEDO, Duke of (1508-1582),
a Spanish statesman and general under
Charles V and Philip II. He is remembered
chiefly for his bloody and tyrannical govern-
ment of the Netherlands, wMeh had revolted,